As shown in U.S. Pat. No. 3,400,093 issued Sep. 3, 1968 to Irving Feinberg, known methods for incorporating pesticides into water-based systems have been unsatisfactory in that the pesticides tend to settle out and do not remain uniformly dispersed. Feinberg proposed to solve that problem by emulsion polymerization of monomers in the presence of the pesticide. However, certain pesticides, such as chlorpyrifos and chlorpyrifos-methyl, tend to hydrolyze if heated to polymerization temperatures for extended periods of time and, in addition, the presence of a pesticide in a monomer will influence the polymerization to some degree, e.g., the rate of polymerization, the conversion and/or the molecular weight of the polymer.
Kangas, in U.S. Pat. No. 4,303,642 issued Dec. 1, 1981, proposed to solve the above problems by adding the pesticide to a finished latex wherein the polymeric particles were in a size range of from 0.03 to 20 microns, and increases in pesticide efficiency were, indeed demonstrated, although optimum stability and transfer through soil were not obtained.
Rogiers and Bognolo, in a paper presented at the Sixth International Congress of Pesticide Chemistry, Ottawa, Canada, Aug. 10-15, 1986, reported on the stabilization of an Ethirincol suspension concentrate with a graft stabilizer of a polymethylmethacrylate-polymethacrylic acid grafted with polyethylene oxide.
T. J. Chen, in U.S. Pat. Nos. 4,199,363 and 4,203,716, discloses a process for uniformly dispersing hydrophobic materials through hydrophilic colloid layers, such as photographically useful layers containing gelatin.
Soil pesticides are usually incorporated into the soil mechanically or are spread on the soil surface to be leached into the soil by rainfall. In either case, the pesticide may not be able to function properly because it becomes immobilized at the point of application. This will certainly be the case for large hydrophobic molecules and the problem is compounded further if the carrier is itself a large hydrophobic particle.